Impaired functional and hemodynamic response to graded exercise testing and its recovery in patients with subclinical hyperthyroidism

To evaluate the functional and hemodynamic responses during exercise and its recovery in patients with subclinical hyperthyroidism (SCH). A cross-sectional study was carried out with 29 patients on TSH-suppressive therapy with levothyroxine for thyroid carcinoma and 35 euthyroid subjects. All volunteers underwent a cardiopulmonary exercise testing on a treadmill and functional and hemodynamic variables were measured during exercise and its recovery. SCH patients showed impaired functional response to exercise, marked by lower values for oxygen consumption and exercise duration in addition to premature achievement of the anaerobic threshold. Heart-rate and blood pressure recovery immediately after exercise were slower among SCH patients when compared to euthyroid subjects. SCH is associated with impaired functional and hemodynamic responses during exercise and its recovery.